Method and apparatus for forming twisted tooth lock washers



July 5, 1966 A. CHIARUGI METHOD AND APPARATUS FOR FORMING TWISTED TOOTH LOCK WASHERS 5 Sheets-Sheet 1 Original Filed Aug. 14, 1961 INVENTOR.

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METHOD AND APPARATUS FOR FORMING TWISTED TOOTH LOCK WASHERS Original Filed Aug. 14, 1961 3 Sheets-Sheet 3 United States Patent 3,258 796 METHOD AND APPARATUS FOR FORMING TWISTED TOOTH LOCK WASHERS Anthony L. Chiarugi, Bartlett, Ill., assignor to Illinois Tool Works Inc., Chicago, 11]., a corporation of Delaware Original application Aug. 14, 1961, Ser. No. 131,183, now Patent No. 3,149,655, dated Sept. 22, 1964. Divided and this application May 12, 1964, Ser. No. 366,879 6 Claims. (Cl. -85) The present invention relates to a novel method and apparatus for producing lock washers, and more specifically to a novel method and apparatus for producing twisted tooth or prong type lock washers. This is a division of my copending application S.N. 131,183, now Patent No. 3,149,655, filed August 14, 1961.

Lock washers of the type including a plurality of generally radially disposed prongs extending from an annular body section and twisted about their radial axes so as to present locking teeth have long been commercially available. Numerous variations of such washers have been suggested many of which have been considered to be generally satisfactory.

When producing heretofore proposed twisted tooth type lock washers, one procedure which has been generally followed is to provide a flat washer blank having flat teeth or prongs and then to twist the prongs by engaging them with twisting dies having generally pointed prong engageable teeth. This procedure and such dies have in many instances heretofore been considered to be generally satisfactory. However, in view of the present invention it appears that such heretofore proposed procedures and dies resulted in the addition of unnecessary costs to the finished product primarily as a result of a relatively rapid wearing of the dies requiring replacement thereof and the failure to obtain a significant portion of the locking action or holding power available from a given amount of washer stock material.

It is therefore an important object of the present invention to provide a novel method and means for producing a lock washer whereby substantial and significant economies in production and material costs may be obtained.

A more specific object of the present invention is to provide a novel method and apparatus for producing a lock washer which is constructed so that increased locking or holding power for a given size washer may be obtained or, if desired, a desired locking or holding power may be obtained with a washer of a given size made from thinner and less expensive stock material.

A still further specific object of the present invention is to provide a novel method and apparatus for producing a washer of the twisted tooth or prong type which is constructed so as to provide for greater resistance to collapsing of the teeth and increased tooth edge engagement when the washer is clamped between opposing surfaces of a work structure.

A further specific object of the present invention is to provide a novel die structure for making twisted tooth type lock washers, which die structure is of economical construction and has a useful working life substantially longer than that of certain generally similar die structures heretofore in use.

Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings wherein:

FIG. 1 is a plan view showing a twisted prong or tooth lock washer produced in accordance with features of the present invention;

FIG. 2 is an enlarged edge elevational view of a lock washer produced in accordance with features of the present invention;

FIG. 3 is a sectional view taken generally along line 33 in FIG. 2;

FIG. 4 is a fragmentary sectional view taken generally along line 4-4 in FIG. 5;

FIG. 5 is a further enlarged fragmentary perspective view showing features of the novel washer structure in greater detail;

FIG. 6 is a view showing the cross sectional configuration of a tooth or prong generally along line 66 in FIG. 5;

FIG. 7 is a view showing the cross sectional configuration of the prong generally along line 7-7 in FIG. 5;

FIG. 8 is a perspective view showing a set of dies incorporating features of the present invention;

FIG. 9 is an end view of the lower dies shown in FIG. 8;

FIG. 10 is a sectional view taken along line 1010 in FIG. 8;

7 rating features of the present invention engage the teeth or prongs for forming them in accordance with the pres ent invention;

FIG. 13 is a sectional view taken generally along line 13-13 in FIG. 12;

FIG. 14 is a plan view showing a washer incorporating a modified form of the present invention;

FIG. 15 is a plan view showing a washer embodying another modified form of the present invention;

FIGS. 16 and 17 are respectively similar to FIGS. 9 and 10 and show a modified die structure for forming the washer of FIG. 15;

FIG. 18 is an enlarged edge view of the washer shown in FIG. 15;

FIG. 19 is an enlarged fragmentary perspective view of the washer shown in FIG. 15

FIG. 20 is a view showing the sectional configuration of a washer tooth taken along line 2020 in FIG. 19; and

FIG. 21 is a view showing the sectional configuration of a washer tooth or prong taken along line 2121 in FIG. 19.

Referring now more specifically to the drawings wherein like parts are designated by the same numerals throughout the various figures, a washer 20 incorporating features of the present invention is shown in FIGS. 1-7, 12 and 13. The washer 20 is formed in the manner which will be described in detail below from sheet material stock such as steel and is provided with an annular body portion 22 having opposite or inner and outer margins 24 and 26. Prongs 28 extend from one of these margins and in this embodiment roots 30 of the prongs are integrally joined to the outer margin 26 of the body portion.

The prongs 28 are preferably substantially uniformly spaced around the body portion 22 and they extend so that their central or longitudinal axes are respectively disposed substantially radially with respect to the annular body section 22. Each of the prongs 28 is twisted and formed in a manner which will be described in detail below so as to locate opposite generally longitudinally or radially extending edges 32 and 34 thereof axially of opposite sides of the body portion 22. Thus, the edges 32 and 34 provide locking teeth engageable with a fastener such as a nut or a screw and a workpiece when the washer is clamped between the fastener and the workpiece.

In accordance with features of the present invention, the washer is provided with pairs of embossed or rib like areas 36 and 38 associated with each of the prongs 28. The areas or rib like means 36 and 38 of each pair are respectively substantially disposed at opposite sides of the radial axis of their associated prong as shown best in FIGS. 5-7. Furthermore, these areas are embossed or formed in opposite directions. More specifically, as shown best in FIGS. 6 and 7 each area or rib like means 36 has a cross-sectional configuration with a hollowed or concave surface 40 at one side of the washer and a rounded or convex surface 42 at the opposite side of the washer while each of the areas or rib like means 38' is oppositely formed with a hollowed or concave surface 44 at the same side of the washer as the surface portion 42 of the area 36. The area or rib like means 44 also has a rounded or convex surface 46 at the same side of the washer as the concave surface portion 40 of the area 36.

In FIG. 11 a blank 48 from which a washer 28 is to be formed is shown in a flat condition. In other words, FIG. 11 shows the blank prior to the twisting and forming of the prongs. Thus, this view provides a clearer showing of the fact that in this embodiment the opposite edges 32 and 34 of the prongs converge with respect to each other from relatively broad roots toward relatively narrow terminal free ends of the prongs. With prongs of this structure, the embossed areas or rib means 36 and 38 are preferably formed so that longitudinal center lines thereof diverge with respect to each other from the outer terminal ends of the prongs toward and across the roots of the prongs. As shown best in FIG. 5, the rib means 36 and 38 extend from the outer free terminal ends of the prongs through the roots 30 at the outer margin 26 of the body portion and into the body portion to points 50 and 52 spaced radially inwardly a substantial distance from the outer body portion margin 26 and still spaced radially outwardly from the inner body portion margin 24.

As previously indicated the rib means 36 and 38 associated with each prong are disposed in generally diverging relationship in a direction extending from the outer ends of the prongs inwardly and, more specifically, the rib means 36 and 38 extend generally along their adjacent prong tooth edges 32 and 34. Thus, the radially inner end portion of the rib means 38 associated with each prong is adjacent and converges toward the radially inner end portion of each rib means 36 associated with an adjacent prong as shown best in FIG. 5. The circumferential spacing of the prongs is such that such converging inner end portions of the rib means 36 and 38 of adjacent prongs merge with each other and provide the margin 26 of the washer body portion with an undulated configuration similar to that of a sine wave as shown best in FIG. 4. This undulated outer marginal section of the body presents abutment surfaces 54 and 56 at the high points of their respective rib means 36 and 38 axially of opposite sides of imaginary bounding planes of the flat inner margin 24 of the washer body. The abutment surfaces are engageable with a fastener such as a screw or nut and a workpiece when the washer is clamped between the fastener and the workpiece for providing relatively rigid abutment means for resisting complete collapsing of the prongs.

The rib means 36 and 38 not only provide the aforementioned abutment means surfaces 54 and 56, but by extending along the prongs and particularly in diverging relationship across the junctions between the roots of the prongs and the margin of the washer body-portion, the rib means also provide the prongs themselves with a relatively great resistance to collapsing so that the strength and locking power of the washer is materially increased. Furthermore, the roots of the prongs are undulated in the same manner as the outer margin 26 of the body portion so that the edges 32 and 34 of the prongs at the root locations are disposed axially of opposite sides of the body washer for engagement with opposing clamping surfaces of a work structure and a fastener. In other words, substantially the entire lengths of the edges 32 and 34 are presented for engagement with the opposing clamping surfaces so as further to increase the locking effectiveness of the washer. As indicated above, the inner end portions of the rib means 36 and 38- terminate short of the inner margin 24 of the washer body. Thus, the abutment surface means 54- and 56 gradually decrease in effective height from the outer margin 26. Furthermore, the abutment surface means 54 and 56 are somewhat rounded as they merge into the substantially planar opposite side surfaces of the washer body in the vicinity of the inner margin 24. This structure aids the abutment surface means in resisting collapse under clamping pressures when the washer is secured between a fastener and a Work structure.

In accordance with further features of the present invention, die members 58 and 60 are provided for forming the washer 20 from the blank 48. The dies 58 and 60 are substantially identically formed and oppositely disposed when in use as shown in FIGS. 8, 12 and 13. Thus, each of the die members includes a shank or body portion 62 having a plurality of teeth or ribs 64 formed at one end thereof. As shown best in FIG. 12, each of the ribs 64 has a generally triangular cross-sectional configuration defined by opposite side or flank surfaces 66 and 68. The angles of inclination of the flank surfaces 66 and 68 With respect to a plane perpendicular to the longitudinal axis of the die body 62 are unequal. The flank surface 68 is disposed at an acute angle with respect to said plane approximately equal to the desired angle of twist of the washer prongs while the flank surface 66 is arranged at a larger acute angle with respect to the plane. Thus, the crest 70 of each rib at the junction between the flank surfaces 66 and 68 is offset so as initially to engage a prong during a washer forming operation along a line laterally offset from the radial axis of the prong.

In accordance with features of the present invention, the crests 7t) of the ribs or teeth 64 are rounded in crosssection as shown best in FIG. 12. The ribs extend from the peripheral surface of the die body generally toward and substantially to the center of the die body, and the crests 70 progressively decrease in heighth from the periphery of the body toward the inner ends of the ribs, as shown best in FIG. 13. Roots 72 of the ribs are also inclined with respect to an imaginary plane perpendicular to the longitudinal axis of the die body and, as shown best in FIG. 13, the roots 72 are of maximum depth at the periphery of the die body and progressively decrease in depth forward the inner ends of the ribs. The formation of the ribs or teeth 64 and particularly the inclination of the crests 70 are such as to accomplish twisting of the washer prongs in the manner described above and engagement and forming or embossing of the outer marginal portion of the washer body and without substantial engagement and forming of the inner margin of the washer body.

. As shown best in FIG. 9, the ribs 64 are arranged generally radially but at the same time they are arranged so that their crests 70 are not truly on radial lines but are substantially tangent to a small centrally located circular area 74. Preferably, this area 74 is cut away as shown best in FIGS. 9 and 13 so as to facilitate construction of the dies. It is to be noted that when the die member 60 is arranged oppositely from the die 58, the crests 70 of the die member 68 will be inclined with respect to a radial line oppositely from the crests 70 of the die member 58 as can be readily seen by comparing FIGS. 9 and 10. Thus, the ribs or teeth elements of the die members are disposed for forming the rib means or embossed areas at the opposite sides of the washer in the above described relatively-diverging relationship.

FIG. 14 shows an internal tooth type lock washer incorporating features of the present invention. Except for the arrangement of the teeth or prongs internally rather than externally, this washer is constructed in substantially the same manner and includes the same features of the washer 28 described above as indicated by the application of identical reference numerals with the sutfix a added to corresponding elements.

FIGS. 15 through 21 show another embodiment of the present invention which is similar to the structure described above as indicated by the application of identical reference numerals with the sufiix b added to corresponding elements. In this embodiment the ribs or teeth 64b of the die members 58b and 60b extend radially rather than tangentially to a small centrally located circle as shown in FIGS. 16 and 17. This structure further simplifies production of the die members and may result in substantial manufacturing economies.

In this embodiment the rib means or embossed areas 36b and 38b at opposite sides of the washer teeth or prongs 28b are also formed so that they extend substantially radially. As shown best in FIGS. 19 and 21, the radially extending rib means or embossed areas 36b and 38b terminate short of the free or outer extremities of the prongs so that the extremities are substantially rectangular or flat for aggressively presenting the tooth edges 32b and 34b thereof.

While the preferred embodiments of the present invention have been shown and described herein, it is obvious that many structural details may be changed without departing from the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A method of making lock washers of the type described comprising providing a substantially flat sheet material blank having an annular body portion and a plurality of spaced generally radially extending prongs having roots integrally joined to a margin of the body portion, embossing circumferentially adjacent areas of each of said roots generally axially in opposite directions, and simultaneously twisting said prongs about their radial axes.

2. A die for making lock washers of the type described comprising :a shank portion, and a plurality of integral ribs on one end of said shank portion, said shank portion in the vicinity of said ribs having a predetermined diameter, said ribs extending inwardly from adjacent the periphery of said shank portion and having crests extending from said periphery to a circle centrally located with respect to said shank portion and having a diameter which is only a small fraction of said predetermined diameter, each of said ribs having opposite flank surfaces extending from roots of the ribs to the crests thereof at different angles relative to a plane perpendicular to the central axis of said shank portion, and said crests of said ribs also being disposed at an angle with respect to said plane and progressively increasing in height from said central circle toward the periphery of the shank portion.

3. A die, as defined in claim 2, wherein the crest portions of said ribs have a rounded cross-sectional con figuration.

4. A die, as defined in claim 2, wherein said roots of said ribs progressively increase in depth from said central circle toward the periphery of said shank portion.

5. A die, as defined in claim 2, wherein said crests extend substantially tangentially to said circle.

6. A die, as defined in claim 2, wherein said crests extend radially from said circle.

References Cited by the Examiner UNITED STATES PATENTS 1,915,612 6/1933 Olson 10--86 2,150,126 3/1939 Olson 10-86 2,234,194 3/1941 Poupitch 1086 2,380,584 7/1945 De Loe 10-85 2,568,440 9/1951 Friedman 10-85 2,871,492 2/ 1959 Sciullo 10-86 3,141,182 7/1964 Lanius 10-86 WILLIAM W. DYER, IR., Primary Examiner.

F. T. YOST, Assistant Examiner. 

2. A DIE FOR MAKING LOCK WASHERS OF THE TYPE DESCRIBED COMPRISING A SHANK PORTION, AND A PLURALITY OF INTEGRAL RIBS ON ONE END OF SAID SHANK PORTION, SAID SHANK PORTION IN THE VICINITY OF SAID RIBS HAVING A PREDETERMINED DIAMETER, SAID RIBS EXTENDING INWARDLY FROM ADJACENT THE PERIPHERY OF SAID SHANK PORTION AND HAVING CRESTS EXTENDING FROM SAID PERIPHERY OF A CIRCLE CENTRALLY LOCATED WITH RESPECT TO SAID SHANK PORTION AND HAVING A DIAMETER WHICH IS ONLY A SMALL FRACTION OF SAID PREDETERMINED DIAMTER, EACH OF SAID RIBS HAVING OPPOSITE FLANK SURFACES EXTENDING FROM ROOTS OF THE RIBS TO THE CRESTS THEREOF AT DIFFERENT ANGLES RELATIVE TO A PLANE PERPENDICULAR TO THE CENTRAL AXIS OF SAID SHANK PORTION, AND SAID CRESTS OF SAID RIBS ALSO BEING DISPOSED AT AN ANGLE WITH RESPECT TO SAID PLANE AND PROGRESSIVELY INCREASING IN HEIGHT FROM SAID CENTRAL CIRCLE TOWARD THE PERIPHERY OF THE SHANK PORTION. 